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FXAK68 PAFC 021318
AFDAFC

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
518 AM AKDT Sun Jun 2 2024

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)...

A vertically stacked occluded low southeast of Kodiak Island this
morning will continue to move southwest today. Its occluded front
will remain draped over the northern gulf through Monday,
producing steady rain and easterly winds up to 30 kt across the
northern Gulf. A series of upper-level waves and vorticity lobes
will move along the front with one over the southeast Gulf this
morning helping to develop a surface low west of Sitka. The low
will travel along the occluded front, eventually phasing with the
first low before its weakens into an open trough south of Akhiok
for Monday. This secondary low will help to enhance the easterly
winds across the northern Gulf as well as the rainfall from the
eastern Kenai southwest to Kodiak Island. For Kodiak City, an
additional 1.5" of rain could fall by Monday morning with up to
3" for the northern mountains of Kodiak Island.

Shower activity across interior Southcentral will be less
pronounced today as weak upper-level ridging ahead of the upper-
level shortwave over the northern Gulf yields breaks in the cloud
cover along with slightly warmer temperatures.

By Monday, another upper-level shortwave rotating around the
nearly stationary upper-level low over the Gulf will help to push
the occluded front into the Southcentral coast as the shortwave
itself moves inland. The result will be a more southeasterly flow
aloft that will usher in clouds and moisture in the form of
scattered showers. Most of the shower activity will be across the
Copper River Basin and along both the coastal mountains and Alaska
Range. A few isolated showers will also be possible west of the
Chugach and Kenai mountains for the first half of Monday.

Yet another easterly upper-level shortwave looks to move across
interior Southcentral for Tuesday with additional shower activity
from the Copper River Basin to the Mat-Su Valleys. However, there
is still some uncertainty as to the strength and timing of this
feature.

-TM

&&


SHORT TERM FORECAST SOUTHWEST ALASKA, THE BERING SEA AND THE
ALEUTIANS (Days 1 through 3)...

A trough over the Aleutians digs into the Gulf of Alaska through
Monday with high pressure becoming established over the western
Bering Monday and Tuesday. The combination of high pressure over
interior Alaska and low pressure over the Gulf will continue to
direct easterly waves into Southwest Alaska today and tomorrow.
For today, expect off and on showers for parts of the Lower
Kuskokwim Valley, mainly from Sleetmute to Aniak, southwestward
into the Kuskokwim Mountains down to the coast. Afternoon highs
for most locations will warm into the upper 50s with low 60s also
being reached for parts of the Kuskokwim Delta and Lower Kuskokwim
Valley.

Morning satellite shows breaks in clouds across over Greater
Bristol Bay and over parts of the Western Alaska Range. These
breaks are expected to shift westward through this afternoon as
additional Pacific moisture and associated clouds spill over the
Western Alaska Range. As a result, the best chance for weak
instability developing today will stretch from across the Middle
Kuskokwim Valley into the Kuskokwim Mountains where some isolated
lightning will be possible. Low pressure over the Gulf will begin
to move east on Monday with more breaks in cloud cover over the
Western Alaska Range and portions of Greater Bristol Bay. The
threat for wet thunderstorms and isolated lightning will likewise
shift east as well.

The ridge of high pressure over the western Bering becomes more
amplified on Monday. This and the departing low into the Gulf will
clear the way for northerly flow to develop from the Chukchi Sea
all the way into the Aleutians. Forecast models have consistently
shown the arrival of one or two lows diving southward along the
coast of Alaska with much cooler temperatures by late Tuesday. At
or just above freezing temperatures will be possible into the
Kuskokwim Delta coast by Tuesday afternoon. Drier conditions
associated with the arctic intrusion should preclude any
precipitation, though will certainly be worth watching over the
next couple of days.


-BL

&&


.LONG TERM FORECAST (Days 4 through 7) Wednesday through Saturday...

The midweek upper level forecast opens with a pair of lows
stretching across the Southern portions of the state. The Eastern
Gulf low weakens and tracks through to the Southwest Gulf before
dissipating for Saturday. The Bering low center oscillates between
Bristol Bay and the Central Aleutians, and remains the most
persistent feature through the long term. Some additional energy
out of the Arctic through the Bering Strait helps pull the center
over the Central Aleutians. Jetstream support remains over the
North Pacific. A clustered GFS/ECMWF/CMC ensemble maintains the
best levels of confidence through the forecast period. The upper
level ridge over the Eastern Mainland supports surface thermal
troughs through the weekend.

Weak Southeasterly flow across Southcentral continues to pump
moisture inland to the Alaska Range. Most precipitation will be
showery, with best chances for convection in the Eastern Interior
and Copper River Basin. Almost direct onshore flow continues more
steady rainfall over Kodiak Island and the Alaska Peninsula. Gusty
Northerly surface winds are expected in the Eastern Bering
through Thursday. A number of surface features rotating over the
Bering brings the more active weather across the Pribilofs and
Aleutians.

- Kutz

&&


.AVIATION...

PANC...Gusty southeasterly winds out the Turnagain Arm will likely
develop this afternoon and evening. Otherwise, expect VFR
conditions and light winds to prevail throughout the rest of the
TAF period.

&&


$$